Binary Tree Right Side View

Standard tree-from-the-right view problem, but reported with the extra constraint of building the input tree yourself and writing all test scaffolding inside the round. Requirements Given the root of a binary tree, return the values of the rightmost node at each level, ordered top-down. def rightSideView(root: Optional[TreeNode]) -> List[int]: ... The reported round adds two operational constraints: You must define the TreeNode class yourself. You must construct the test input tree manually in your editor and run your own tests. Notes Standard BFS solution: level-order traversal, take the last element of each level. O(n) time, O(w) space. Alternative DFS: traverse right-first, record the first node seen at each depth into a per-level dictionary. Also O(n) time, O(h) space. Common bug: confusing "right side view" with "rightmost leaf path" — the right side view picks the rightmost node at each level, which may not be a leaf. The tree-construction overhead is non-trivial in the time budget — practice a build_tree(values_level_order) helper that handles None placeholders. Preparation Write both BFS and DFS solutions; some interviewers ask for both. Build a TreeNode + build_tree helper from memory in under 3 minutes; the test scaffolding eats real time otherwise. Drill a couple of test cases including: skewed-left tree (right side view is the leftmost path because there's no right subtree), full tree, single node. Be ready to explain why "rightmost" needs level-order, not pre-order, to handle missing right subtrees correctly.